Re: Need urgent help in fixing raid5 array

[Mike Myers <mikesm559@yahoo.com>]

BTW, don't I need to use the --assume-clean option in the create operation to have this work right?

Thanks,
Mike




----- Original Message ----
From: NeilBrown <neilb@suse.de>
To: Mike Myers <mikesm559@yahoo.com>
Cc: Justin Piszcz <jpiszcz@lucidpixels.com>; linux-raid@vger.kernel.org; john lists <john4lists@gmail.com>
Sent: Monday, January 5, 2009 2:53:43 PM
Subject: Re: Need urgent help in fixing raid5 array

On Tue, January 6, 2009 9:22 am, Mike Myers wrote:
> Thanks!  I see what you are doing here.  So since none of these commands
> actually change the underlying data, if I get the order right. the array
> will come up and the LVM superblock will be visible, and then I can try
> and bring the filesystem online?  If I get the order wrong, I can just try
> it again with another combination.  Do I have that right?

Exactly, yes.

>
> I should probably print out all the existing metadata and save it since
> the data will be wiped out by the create.

Certainly a good idea.

>
> How could the drives get the bad metadata on them>  I've played with
> software raid for about 4 years and have seen seen something this strange.

I really cannot think how they could get the particular bad metadata that
they did.  "mdadm --add" will change the metadata, but only to make the
device appear to be a spare, which isn't the case here.
"mdadm --assemble --force" can re-write the metadata, but again I cannot
imagine it making the particular change that has been made.  Maybe there
is a bug in there somewhere.

NeilBrown